combination

Thanks for the reply, but your method leaves duplicate choices. This question came from an state-sponsored math exam and the correct response is 495. I just need to find the formula for future reference.

Thanks for the reply, but your method leaves duplicate choices. This question came from an state-sponsored math exam and the correct response is 495. I just need to find the formula for future reference.

The question is vague. But the given answer implies a multi-set.
The number of ways to put K identical units into N different cells is .
Here the choices are identical and the pizzas are different.